Communication system



Mafh 5, '1940 H. J. NlcHoLs 2,192,603

n couMUNIcATIoN SYSTEM Originai Filed Jan. 29, 1954 2 Sheets-Sheet 1 PRI/mm IN V EN TOR.

March 5v, 1940. H, NICHOLS Y l2,192,603

COMMUNICATION SYSTEM l Original Filed Jan. 29, 1934 2 Sheets-Sheet 2 I l: sw

Patented Mar. 5, 1940 COMMUNICATION SYSTEM Harry J. Nichols, Binghamton, N. Y., assignor York to International Business Machines Corporation, New York, N. Y., a corporation of New Original application January 29, 1934, Serial No. 708,767, now Patent No. 2,104,571, dated January 4, 1938. Divided and this application April 16, 1937, Serial No.4137,204

This invention relates to synchronous communication systems and particularly to single impulse printing telegraph systems, and the pres'- ent application is a divisional case of the copending application, Serial No. 708,767, filed January 29, 1934, now Patent No. 2,104,571, granted Jan.

The present application relates specifically to the motor control circuits and therefore has for its object to provide a novel operating method in printing telegraph systems, whereby the'operator at the sending machine can initiate operation of the receiving machine, establish proper conditions of synchronism and thereafter controlthe printing operations of the receiving machine.

Further and other objects and advantages will be hereinafter set forth in the accompanying specification and claims, and shown in the drawings, which by way of illustration show what is now considered to be the preferred embodiment of the invention.

In the drawings: n

Fig. l shows in diagrammatic form thecircuits and apparatus which, Vtogether with the typewriter or printer typing mechanism, comprise a complete communication unit. The circuits are shown in the receiving condition, or more precisely, in readiness-to receive.

Fig. 2 shows in diagrammatic form the particular parts of the circuit and apparatus used to control the key board and to prevent the transmission of false signals.

Fig. 3 is a diagram showing the arrangement of circuits, apparatus, and switches whereby automatic starting of the receiving machine is accomplished.

in the several figures, like characters represent like parts.

General description For purposes of description and as illustrative of a preferred embodiment of the invention, a

' complete communication unit is hereinafter described as comprising a typewriter, a typewriter v,

control unit, and a distributor unit. The typewriter control unit is preferably mounted underneath and inside the typewriter frame. The distributor unit is preferably housed in a. case located near the typewriter. The two units are conveniently connected electrically by a multiple conductor cable. The complete communication units may be used in pairs, one unitsending while the other receives andvice versa, or they may be connected in such a manner that the sending' unit controls N0. 672,161 filed May 22, 1933.

a group of receiving units. Units may be connected for communication purposes by means of ,general communication systems, such as a'telegraph, telephone, or radio system, or simply by a.

pair of wires, orone wire and ground.

In Fig. 1, the apparatus comprising the typewriter control unit is included within the dotdash rectangle; all other apparatus is includedin the distributor unit.

The apparatus shown in Fig. 1 performs the functions of transmitting and receiving synchronizing and printing signals, and utilizing lthese signals, and responsive local impulses, for various starting, synchronizing, selecting, and control purposes. The local impulses are distributed to their proper distributor. p

Referring now to Fig. 1 in detail, the rotary distributor vI 5 consists of a seriesvof insulated metallic segments I6 and a solid metallic ring I'I mount- .ed on a-suitable disc of insulating material (not shown). A rotary contactor I8 is frictionally driven by drive motor I9 and contacts each segment once during each revolution in a well un derstood manner. The drive motor I9 must be of exactly uniform speed, or suitable governing means must be employed to obtain a highly uniform speed.

The rotary contactor I8 is shown in the restV winding 22 and a high impedance winding 23 connected in series aiding relation. Across the tercircuits bythe rotary minals of winding 23 is connected vs toring-conYK denser 24.- Release magnet 20 is of the quick ,Y

acting, slow release type which respondsquickly to a short current pulse, but holds for a. protracted'y period, hence if supplied with properly timed im-l pulses, continues to hold-in the operatedposition so long as, such pulses are regularly received, but drops out shortly after thepulses cease, or in case the pulses are too greatly diminished. An `improved relay or magnet of` this type, which may be termed a pulse sustained relay, is described'in detail in my copending patent application, Serial v The power for transmissionpurposes 'and for he operation of the various relays and magnets' is obtained from any suitable direct current source, preferably from a rectier assembly as shown.

` The output of the rectier is applied to the terminalsof a four section voltage divider 44, as

shown. The positive bus 42 is connected to the positive terminal of voltage divider 44, and the negative bus 40 to the negative terminal. The zero bus 4| is connected to the zero or ground terminal between sections44a and 44h of voltage divider 44, section 44a thus furnishing in a well understood manner negative bias for the grid |313 of electronic relay |30.

The elements of electronic relay |30, which is of the grid controlled, gaseous discharge type are the grid |33, the cathode |34, and the anode or plate |35, all contained in an envelope |32 containing gas or vapor at low pressure, as is well understood.

In series with the anode-cathode circuitof relay |30 is the cut-off relay |10, connected as I plate current must be cut off, or else the plate must be rendered negative in respect to the cathode. It is preferred to cut off the plate current after a properly timed interval by utilizing cutoff relay |10 to open contacts I13-|14. The variable resistor |12 permits of very exact timing of the cut-olf interval, and the location of the relay' in the circuit as shown is found to give quick and reliable de-ionization of the electronic relay |30. A spark suppressor arrangement may be con- .Each key lever |58 has associated with it an individual key switch |51, of break-make type, actuated by an individual insulated push rod |55. The armature spring o f each. key switch isfco'nnected to an individual segment, to make springs being connected to the common key-switch bus |38 as shown, while the break springs are` connected to the individual solenoids. A universal bail |53 is positioned below and transversely across the row of key levers, being held in light contact therewith by a retractile spring (not shown). When any key is depressed, bail |53 closes auxiliary switch |54 by means of push rod |55. Auxiliary switch |54 forms a part of the key-latch and non-repeat arrangement.

The key latch I| consists of a pivoted, universal latch bar extending across the ends of all the key levers. the ends of which are provided with a square projection as shown. A retractile spring |83 attached to latch |5| so as to obtain proper leverage normally holds the latch out of engagevinent with the key levers. The key latch magnet Sending circuits and operations Referring to Fig. 1, the transmission of synchronizing signal impulses is accomplished as follows:

Assume that drive motor I9 is operating and 'tending to rotate rotary contactor I8 by a friction nected across contacts |13-I14-as shown to reduce sparking to a negligible degree.

The non-repeat relay |40 is connected in circuit only while sending, and has for its principal function the prevention of the transmission of false signals. It will be explained in detail hereafter in connection with Fig. 2.

The multiple switch relay |50, controlled by send-receive switch |90, provides the automatic switching operations required to change from sending conditions to receiving conditions and vice versa. It is provided with a single winding |6I and five sets of contact springs numbered ||4 inclusive. In order to simplify the diagram, these contacts are shown in their natural locations in the circuit. The winding of relay |50 is connected in'series with the windings of release magnet 20 across section 44d of the voltage divider reducing the voltage across these windings and economizing on holding current.

The start relay 50 is connected across the line on receiving so as to respond to received signals. It is of the pulse sustained type and performs various switching operations to start the receiving, machine automatically. It will be more fully described hereinafter in connection with Fig. 3.

The input transformer 32 is connected to the line on receiving by start relay 50. It applies the signal pulses to the grid of electronic relay |30.

Included in the typewriter control unit is the key solenoid assembly suitably mounted, consisting of a bank of solenoids |58, one for each opdrive but that the contactor is held in the rest position on segment 2 by armature 2| of release magnet 28. To start sending synchronizing signals, send-receive switch |90 is thrown to the S or send position. This completes a circuit from positive bus 42 through winding 22 and condenser 24 of release magnet 20 via contacts |92--I9I of send-receive switch |90, through winding |5I 4of relay |50 to the voltage divider between sections 44e and. 44d. A current pulse through this circuit operates relay l50, breaking contacts 2 8, 5 5, 8 9, ||-|2, and making contacts |2, 4 5, 1-8, |0| I, |3|4. Release magnet 20 is also energized, attracting armature 2| which releases rotary contactor I8. As condenser v24 becomes charged a small steady current limited mainly by the resistance of windings 23 and |8| flows through these windings providing sufdcient holding current to hold relay |50 and magnet 2l in the operated condition. A strong operating pulse followed by low holding current is thus provided'.

On being released by armature 2|, contactor I8 is set in rotation by the friction drive and takes up the uniform speed of the motor drive shaft.

VWhen contactor I8 reaches segment I, a circuit is completed from positive bus via contacts 8--1 through inductance |51, via contacts 4-5 to segment I; thence via contactor I8 to ring I1 and via ,141" of non-repeat relay l |48 which is included in the` printing signals, hence the amplitude and wave form of the.. synchronizing Signals'and printing signals are substantially identical. y w,

To commence sendingl printing signals, sendreceive switch |90 is thrown to the S position,

and synchronizing signals are sent' to the line for a few seconds to permit the receiving machine to come to synchronism as hereinafter described. Printing signals may then be sent by depressing the typing keys of the ltypewriter as for ordinary typing.

Referring to Fig. v2, and assuming that key A is struck, a printing signal is transmitted as follows: As the key is depressed, the middle and lower contacts of its .own particular key switch are closed, thus connecting sending bus |38 to a particular segment, in this case to segment 4. When rotary contactar I8 arrives at segment 4, a circuit is completed from positive bus 42 through winding |41 of non-repeat relay |40 via contacts |4||42 of same, to send bus |38, via contacts of closed key switch |51 to segment 4, via'contactor i8 to ring, thence via contacts 2| and` to line and return tol zero bus via ground. A current pulse flows through this circuit including the line, its duration being determined by the time of contact of contactor |8 with the connected segment. Such aperiodic signal impulses, distinguished in respect to the time interval from the preceding synchronizingsignal, constitute the printing signals.

concurrently, as the key lever nears the bottom of. its stroke, the printing mechanism (not shown) of the typewriter is tripped, and the typewriter immediately types the proper character to furnish a local copy of the message.

Key latch and non-repeat arrangement Instantly upon the depression of a printing key, the key latch arrangement is operated as follows: Each time a key 'is depressed, universal bail |53 closes the contacts of auxiliary switch |54 by means of pushrod |55. The lower spring of the auxiliary switch is connected to ground and the upper spring is connected via contacts |94 |93 to contact |45 of non-repeat relay |40. Upon closing of the auxiliary switch contacts, a circuit is completed from ground via contacts of auxiliary switch |54' and contacts |94-I93 and |45|44 through winding |52of latch magnet |50 to tap 44f of voltage divider '44. A current pulse through thecircuit just traced operates latch magnet 50 which by means of spring link |8`4 and crank arm |89 quickly hooks the pivoted latch member |5| over the end of the depressed key lever, latching .it down. This is done so quickly that the finger can be removed from the struck key with great rapidity without danger of premature release of the key lever.

As illustrated in Fig. 2, the latch member not only serves to hold down the vdepressed key, but also serves as an interlock to hold all other keys against being depressed, thus guarding against depressing a second `key before the' printing signal from the connected Lsegment is sent to the line. This arrangement has the advantages of not requiring additional interlocking means to obtain this feature, and also in that the interlocking feature only comes into play during sending, the key board being entirely freel when receiving. As a consequence, "less actuating force for the key levers is required permittin smaller key solenoids to be employed- Thegprinting impulse previously described. in

u addition to sending a printing signal to me une,

also performs an important function'in the keyrelease and non-repeat operations. The printingimpulse flowing through winding |41 energizes non-repeat relay |40,.which operates; opening contacts |4||42 and |44,-|45, and closing contacts |42|43 and |45-|46. Opening contacts |4||42 disconnects winding |41 which is too low in resistance to place directly across the line. Opening contacts |44|45 `cuts holding current of! winding |52 of latch magnet |50 which releases, thus permitting retractile spring |83 to draw'latch IBI away from the key levers, thus releasing all keys insofar as the latch arrangement is concerned. It is possible, however, that a key may be inadvertently held down by the nger after being released byv the latch, and in this event, it is necessary to prevent false repeat signals from being sent to the line. Therefore,

when contacts |45|48 are closed, send bus |38 |54 to ground. yW'hen the depressed key is re. leased, auxiliary switch |54 is opened, taking holding current off the non-repeat relay, which releases and opens contacts |43|42 and |4'6-|45. This completes the cycle, and leaves all sending circuits in normal condition.

It will be noted that the key latch |5| serves as a key board lock during the brief but variable interval from the instant a key is depressed until the signal impulse is transmitted by rotary contactor |8, whereupon the non-repeat relay cuts off the current from the latch magnet. Simul-r taneously, the non-repeat relay grounds the send bus and .hence any connected segment, preventing further signals being sent to the line until ali keys are released.` The result is that only one signal can be sent for each cycle of operation of a key lever. This constitutes the non-repeat feature. In case continued repeat signals from a key are desired, it is only necessary to connect the key latch switch of that particular key to positive bus instead of to the send bus, which exempts that particular keyfrom the non-repeat feature.

In normal operation, the keys are depressed and released quickly, and the key board is released Vfor further writing practically instantly when the signal is sent to the line.

Starting circuits and operations f Referring toFigs. 1 and 3, andmorea particularly to Fig. 3, the apparatus primarily involved ln receiving both synchronizing and printing signals comprises start relay 50, the primary winding 33 of input transformer 32, and their associated circuits and switches. Start relay 50, prefvrelease magnet 20, start relay 50 need not be as powerful, since it is required only to operate its own contact springs, and need not respond to the first pulse received. Likewise, it is not essential that startrelay 50 have separate operating g and holding windings, although there is in some switch relay |60 as indicated above, or manually by send-receive switch |90, as may be preferred.

Contacts I3-I4 function in the starting of drive motor I3 when initiating sending conditions.

The operation of the automatic start arrange- .o ment'is as follows: The incoming signals, as-

sumed to be the synchronizing' signals, are received at the line terminals 30, 3| and traverse the circuit from terminal 30 via contacts ||I2 via contacts 54-55 through winding 56 and congg denser 58 to terminal 3|. The pulses through this circuit build up the charge on condenser 58 faster than the charge leaks off through winding 51, thus energizing relay 50 which pulls in its armature on a signal pulse, opening contacts 55-54, and closing contacts 54-53, and 52-II. Opening contacts 55-54 removes the short circuit on primary 33, which thus becomes capable of functioning. Closing contacts 53--53 short circuits winding 58, whose impedance is thus re- `moved from the signalling circuit to compensate for the addition of the impedance of winding 33. Closing contacts 52-5I connects power to drive motor I3 and, if required, to the typewriter motor in instances where. electric driven typing machines are employed. It is to be noted (Fig. 3) that a two-way manual switch SW is provided for the typewriter motor, so that this motor may be started automatically if not already running.

So long as signals are regularly received, relay 50 remains operated; if signalling is discontinued. or interrupted, the charge oncondenser 58 is not replenished, and relay 50 releases, restoring all circuits to initial conditions. This completes the cycle of operations of the automatic start arrangement, which provides means for starting up the receiving machine in the absence of attendants, after which messages may be received in the usual manner. It also provides for shutting down the receiving machine during idle periods.

It is to be noted that the arrangement illustrated assumes that power is already turned on the rectifier apparatus and also on the cathode of theelectronic relay |30. This is the preferred arrangement where messages are being sent'back and forth frequently, since there is no need to wait until the rectifier and electronic relay tubes.

are warmed up before starting transmission. Where messages are sent infrequently, or the warm up period is negligible, or the saving by not having the tubes -lighted is a consideration, start relay 50 can be utilized to turn current on the rectifier, or electronic relay, or both, as desired. Such. variations in switching arrangements to meet various operating conditions will be evident -to those skilled in th'e art and are clearly within the scope of the invention.

Synchronization The operations connected with the sending of f the periodicy synchronizing signals have already beenl described. Referring again to Fig. 1, the operations connected with receiving and utilizing these signals are as follows: The first step is that of establishing synchronism of rotary contactor I3 of the receiving machine with the received synchronizing signals. Since thel periodic synchronizing signals' are sent from a particular segment, termed the synchronizing segment. of the sending machine, it follows that for complete synchronization, the rotary contactor at the receiving machine must arrive at the leading edge of the synchronizing segment each time a synchmrnizing signal arrives from lthe sending mac e.

At the receiving station, the synchronizing signals are received at the line terminals 30 and 3|, and upon the operation of start relay 50 are applied to the primary 33 of input transformer 32. Concurrently, the drive motor is started up, as previously described. 'I'he synchronizing signals through primary 33 induce a voltage across secondary 34 and shunt resistor 35, and with proper polarity, alter the bias voltage on grid |33 and trigger off electronic relay |30, which becomes ionized and conducting, thus permitting a strongcurrent flow in its plate circuit. The contactor I8 being held at rest on segment 2, a circuit is completed from zero bus via contacts II3-I'I4, through relay winding I'II via center tap |36 of power transformer |31 to cathode of relay |30 thence to plate |35, via contacts 3-2 to ring, via contactor I8 to segment 2, via contacts 26-25 through condenser 2l and winding 22 to positive bus. A strong current pulse flows through this circuit, operating release magnet 20 and thereafter cut-off relay |10, which opens contacts F13-|14, terminating the pulse. The armature 2| is quickly pulled in, releasing contactor I8 and opening contacts 25-26. The pulse of current through condenser 2l charges that condenser, providing holding current for relay 20, and preventing the release of armature 2|.

Upon release, contactor I8 is set quickly in motion by its friction drive, and is thereafter rotated at uniform speed by drive motor I9. Contactor I8, having been released from segment 2 in re- I sponse to a pulse occurring concurrently with the passage of the contactor across segment I at the sending station would arrive at segment I before the arrival of the next synchronizing signal, were it not for a slight delay in the operation of relay 20 and a slight amount of slip of the friction drive. Because of these delays, the lead provided by starting contactor I8 from segment 2 enables the contactor to arrive at the leading edge of segment as the next synchronizing signal is received. This synchronizing signal energizes electronic relay |30 as before, but this time the local circuit is completed via segment I, the circuit of segment 2 having been opened at contacts 25--23 by the operation of release magnet 20. The current pulse through the completed circuit replenishes the charge on condenser 2l, maintaining release magnet 20 in the operated position, hence armature 2| does not interfere with contactor I3 winch continues in rotation so long as it arrives on segment I in unison with the synchronizing signal. Means are provided for adjustment of the starting position of contactor I8, and also of the frictional driving force, thus enabling exact timing of the starting revolution to be made. In practice, it is found that with proper adjustments, synchronism is` accurately established on the first revolution. Thereafter, the maintenance of Synchronism depends on the preservation of precisely uniformY speed of the drive motors at the sending and receiving machines. Should, for any reason, unison within approximately one-half segment width be departed from,

vor the incoming synchronizing signals be interrupted beyond a predetermined. interval, contactor I8 is stopped on the rest segment by reason of release magnet 20 dropping out through lack of suilcient holding current. The synchronizing procedure isthen repeated when the next syn-v chronizing pulse is received. Thus Synchronism, if lost, is automatically re-established.

The system of synchronizing herein described is particularly adapted to communication systems to be operated in regions having a common power system of accurately controlled frequency, in which circumstances good results are obtained from synchronous drive motors supplied with power from the common system. As is well understood, the employmentof synchronous motors in such installations assures virtually perfect isochronism, and if the receiving machine is established in the proper phase relation,`synchronism with the sending machine will continue practically indeiinitely. For installationswhere suitable synchronous power is not available, the synchronizing 'system disclosed in my copending application Serial No. 672,161 filed May 22, 193 may be preferred.

ously described and the rotary contactors at the receiving and sending stations being in unison,

printing signals may be sent to the receiving lStation as described in connection with sending oper-3 ations.

Referring to Fig. l, the printing signals when received are applied to primary 33 as previously described, and potential variations from secondary 34 trigger off electronic relay |30 which becomes conducting. A circuit is thus completed from zero bus via contacts I13-I14, through relay winding I1I via center tap |36 of power transformer |31 to cathode of relay |30, thence to plate |35, via contacts 3-2 to ring as before described, and thence via contactor I8 to the segment with which it is in contact. The response of electronic relay |30 to signals being practically instantaneous, and contactor I8 being in unison Wlththe corresponding member at the sending station,

net i |58 whose plunger is attracted, stretching` spring link |84 which pulls down the key lever to which it is attached. 'I'he key lever trips the typewriter or printer mechanism (not shown) printing the selected character. As the key lever nears the end of its downward travel, push rod |55 opens the key switch contacts. Owing, however, to inertia of the key lever and other retarding effects, the circuit'is actually broken by the opening of contacts I1'3-I14 vby cut-01T relay |10 which is preferably adjusted to cut oiI the current just short of the termination of the line signal. With perfect unison, the circuit is broken before contactor I8 leaves the connected segment.

While there has been shown and described and y Pointed out the fundamental novel features of the invention -as applied -t'o a single modiilcation it will be understood that various omissions and substitutions and changes in the forni and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the'invention. Itis the intention, therefore, to belimited only as indicated by the scope of, the followingv claims.

What is claimed is: 1

1. In a motor remote control system.l controlling means producing periodic impulses, transmission means for said impulses, a motor, and relay switching means for-applying power to said motor comprising a relay responsive to said impulses and electrical storing means cooperating with said 'relay to sustain the operation of the relay during the interval between impulses.

2. In apparatus of thecharacter described, a sending station, a receiving station, means at said sending station for sending single periodic impulses of deiinite periodicity, relay means at said receiving station responsive to said periodic impulses to condition the receiving apparatus for reception of printing signals, means operable for a predetermined period greater than the period of said impulses for retaining said relay in operative condition during the sending of saidimpulses and providing for the release of said relay upon interruption of said series of impulses.

3. A system of the character described comprising, in combination, means to transmit periodic control impulses, means to receive saidl impulses including control relay means, a nor'- mally inoperative motor associated with said receiving means, said relay means energized and rendered operative by the said impulses to render the said motor operative, and means cooperating with the relay means to maintain the relay means .operative during theinterval between the arrival Voi? successive impulses. Y

5. A system of the character described comprising, in combination, means to transmit aperiodic character impulses and periodic control impulses., ,means to receive the said impulses'including vmeans adapted to be responsive to and controlled by the character impulses, a normally inoperative motor, means controlled up receipt of the control'impulses to render the motor operative, and means associated with the last mentioned means to control the character impulse responsive means upon operation thereof so as to be responsive to the character impulses.

6. A system of the character described comprising, in combination, means to transmit aperiodic character impulses and periodic control impulses including a plurality of impulse initiating circuits conditioned in succession to transmit the impulses, means to receive said impulses and including a plurality of normally inoperative impulsereceiving circuits adapted to be responsive to said impulses, means responsive to the periodic impulses and operated upon receipt thereof, the operation of said means rendering the plurality of impulse receivingcircuits operative so as to be responsive to the vcharacter impulses and meansto render saidmeans, whlchis operated Y by the periodic impulses, operative during the interval between the arrival oi' successive impulses.

7. A system of the character described comprising, in combination, means to transmit aperiodic and periodic control impulses, means to receive said impulses including normally inoperative rotary means, a plurality of circuits, means responsive to and operated by the periodic control impulses upon receipt thereof to render said rotary means operative thereby rendering the plurality ofcircuits responsive to the aperiodlc control impulses, and means to maintain the rotary means operative'during the interval between the arrival of successive impulses.

8. A system o! the character described comprising, in combination, means to transmit aperiodic and Jperiodic control impulses, means to receive said impulses including a circuit including control means responsive to the periodic impulses, and operated thereby, a normally inoperative motor rendered operative upon operation of the said control means. means to maintain said motor operative during the interval between'the arrival of successive impulses, the operation oi' said control means rendering the circuitresponsive tof and controlled by the aperlodic control impulses.

9. "A systemcf the character described comprising, in combination, a plurality ci typewriters, each having means for sending or responding to aperiodic and periodic-control impulses, including a motor, and'means for placing one typewriter in condition to operate the motor and send out the said impulses and means for putting th other typewriterin condition to respond to the impulses thereby rendering the motor operative upon receipt of` the periodic impulses.

10. A system of the character described comprising, in combination, a plurality of typewriters, each having means for sending or responding to aperiodic and periodic controlimpulses, including a motor, and means for putting one typepulses to maintain the motor operative during the interval between the arrival of successive impulses.

HARRY J. NICHOLS. 

